1. Field of the Invention
The present invention relates to a piezoelectric actuator for use in an ink-jet head or the like, an ink-jet head provided with this piezoelectric actuator, an ink-jet printer, and a method for manufacturing a piezoelectric actuator.
2. Description of the Related Art
Piezoelectric actuators are conventionally known, which drive driven objects by deforming piezoelectrics. For example, this kind of piezoelectric actuator is employed in an ink-jet head such as the one described in Japanese Patent Application Laid-open No. 2003-154646. This piezoelectric actuator has a piezoelectric made of lead zirconate titanate (PZT), lower electrodes and upper electrodes. The lower electrodes are formed on the bottom surface of the piezoelectric, and each of them is associated with one of the pressure chambers in the ink-jet head. The upper electrodes are formed on the top surface of the piezoelectric, and each of them is associated with one of the lower electrodes. A wiring extends from each of the lower and upper electrodes and has an electric contact fitted on its one end. A driver IC (a drive unit) is connected to the electric contacts of the wirings for the lower and upper electrodes and supplies drive voltage to the piezoelectric actuator. When drive voltage is supplied to the piezoelectric actuator, the potential of the lower electrodes differs from that of the upper electrodes. This results in an electric field acting on the piezoelectric, which is sandwiched between the electrodes. The field action deforms the piezoelectric, thereby applying pressure on the ink in the pressure chambers.
However, in the piezoelectric actuator of Japanese Patent Application Laid-open No. 2003-154646, the electric contacts for the respective lower electrodes and the electric contacts for the respective upper electrodes are formed at different heights. Accordingly, it is difficult to directly connect the electric contacts, which are formed at different heights, and the output terminals of the driver IC. This makes it necessary to use a flexible wiring member, such as a flexible printed wiring board (or FPC: flexible printed circuit). However, such a wiring member is generally expensive.
In recent years, there have been needs for higher resolutions in print quality and more compact ink-jet heads. These needs may be met by dense arrangement of the electrodes and electric contacts of the piezoelectric actuator. However, the dense arrangement makes it necessary to use a wiring member having a narrower wiring pitch. Because such a wiring member is more expensive, the cost of manufacturing the piezoelectric actuator is higher.
The electric contacts positioned at different heights and the driver IC may be connected by one wiring member. In this case, the wiring member bends when the electric contacts, which are positioned at different heights, and the connecting terminals of the wiring member are connected. This may decrease the reliability of the electric connection. Alternatively, each of the electric contacts positioned at different heights and the driver IC may be connected by a wiring member. This increases the number of wiring members, thereby increasing the cost of electrically connecting the electric contacts and the driver IC.